Continuing with the theme of accessibility and inclusive design, this week we will explore the topic of color blindness. Approximately 300 million people, or 4.5% of the world's population, have some form of color blindness. While genetics is the main cause, chronic illnesses like diabetes, multiple sclerosis, strokes, certain medications, and advanced age can also contribute. Color blindness occurs when cone cells (photoreceptor cells responsible for color vision in the eye's retina) are either absent or lacking proper function.

Contrary to popular belief, most individuals with color blindness can see some colors. Total color blindness only affects a small percentage of color-blind individuals, with the majority being red/green color-blind to varying degrees. This type of color blindness is called anomalous trichromacy, where a person has all three cone cells, but one is faulty. They have reduced sensitivity to green or red light and sometimes to blue light. As a result, they can partially perceive colors but may have difficulty distinguishing one color from another.

Dichromacy is another type of color blindness where a person only has two functioning cone cells, and the third one does not work at all. Depending on the missing cone cell, they cannot perceive any red, green, or blue light, resulting in those colors appearing grayscale.

Monochromacy is the most severe form of color blindness, characterized by the total absence of functioning cone cells. Individuals with monochromacy cannot perceive any color and see the world in black, white, and grey.

When designing user interfaces, it is essential to understand how color blindness works to optimize designs to not rely solely on color to convey hierarchy or important elements. To learn more about color blindness, visit colourblindawareness.org.